Conductive test probe

ABSTRACT

A conductive probe may include a probe body for communicating with a circuit tester or a jumper. The probe body may be formed of metal and may have a free end. A probe tip may be mounted to the end of the probe body. The probe tip may be formed of thorium-tungsten. The probe tip may be configured for contacting a circuit node.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of and claims priority to co-pendingU.S. patent application Ser. No. 15/707,909 entitled CONDUCTIVE TESTPROBE and filed on Sep. 18, 2017, which claimed priority to U.S. patentapplication Ser. No. 13/730,850 entitled CONDUCTIVE TEST PROBE and filedon Dec. 29, 2012, which issued as U.S. Pat. No. 9,766,269. Each ofapplication Ser. No. 15/707,909 and U.S. Pat. No. 9,766,269 areexpressly incorporated by reference herein. This application is relatedto U.S. patent application Ser. No. 15/334,085 entitled Electrical TestDevice And Method filed Oct. 25, 2016, which is related to pending U.S.patent application Ser. No. 13/404,644 entitled ELECTRICAL TEST DEVICEAND METHOD and filed on Feb. 24, 2012, and to U.S. Pat. No. 7,184,899,issued on Feb. 27, 2007, and which is entitled ENERGIZABLE ELECTRICALTEST DEVICE FOR MEASURING CURRENT AND RESISTANCE OF AN ELECTRICALCIRCUIT, the entire contents of application Ser. No. 13/404,644 and U.S.Pat. No. 7,184,899 being expressly incorporated by reference herein.

FIELD

The present disclosure relates generally to electrical test equipmentand, more particularly, to a conductive probe for a circuit tester or ajumper.

BACKGROUND

The incidence and complexity of electronic circuitry continues toincrease, requiring improvements in the efficiency and functionality ofthe test equipment necessary to diagnose and repair such circuitry. Testequipment such as multi-meters and logic analyzers may generallycommunicate with the circuitry being tested via one or more conductivetest probes. Test probes may be configured to pierce an insulated wireor contact an exposed electrical terminal. Measured parameters mayinclude resistance, voltage, current, impedance, frequency, and digitalwaveforms. In addition, some multi-meters, such as the multi-meterdisclosed in U.S. Pat. No. 7,184,899, have a “power and measure”feature, allowing a technician to probe a circuit, initiate currentsourcing, and simultaneously measure electrical parameters, thusenhancing test efficiency. Some important quality goals for testequipment may include collecting accurate measurements at the requiredresolution without interfering with the operating point of the circuitunder test. Unfortunately, certain design aspects of conventional testequipment may result in poor measurement quality when diagnosing acircuit.

For example, one cause of poor measurement quality may be a test proberesistance that is higher than the required measurement resolution. Forexample, a test probe resistance of 100 milliohms (mΩ) would interferewith the accurate measurement of a circuit resistance requiring aresolution of 10 mΩ by adding 100 mΩ to the measurement result. Testprobe resistance is measured across the conducting length of the testprobe, and does not include the contact resistance occurring between thetest probe and the circuit node. Test probe resistance may depend on theresistivity of the conductor used, on corrosion, and on any damage thatoccurs due to misuse or high current flow. Often, the test probe may befabricated from a metal material having a relatively low resistivity,which may be adequate for conducting moderate current flows of less thanapproximately 1 to 10 amps. For example, brass, an alloy of copper andzinc, has a resistivity of approximately 6-7 μΩ-cm, where metals ingeneral may range from 1-300 μΩ-cm in resistivity. However, manyautomotive circuits require testing with high current flows of fromapproximately 10 to 100 amps or more, which may require the alterationof the geometry or diameter of a brass or steel test probe to insurethat test probe resistance remains small.

Another cause of poor measurement quality may be electrical arcing thatmay occur between the test probe and the circuit node being measured.Arcing may generally begin during the making or breaking of contactinvolving a live circuit in close proximity. A live circuit may occur byeither placing a test probe onto an energized circuit node having avoltage, or by placing an energized test probe onto a non-energized orpassive circuit node, or both. A sustained arc having sufficient heatenergy, i.e., sufficient current, may melt steel. The effect of evenmomentary arcing may be a break down or damage in the conductor materialsuch as brass or steel, causing heating, burning, melting, materialmigration, molecular voids, and a permanent rise in test proberesistance that begins to interfere with the quality of the measurement.Arcing may self-extinguish once the distance between electrical nodesincreases. However, the availability of larger current flows mayincrease the heat energy within an arc, increasing the possibility ofmaterial damage. A test probe susceptible to arc damage may degradeprogressively over time, attracting larger and longer arcs, andincreasing test probe resistance further. Conventional metallic testprobes may therefore require frequent replacement.

Another cause of excessive test probe resistance may be a temporaryheating of the sharpened tip through either arc heating or resistiveheating. During arc heating, initiating an electrical contact may giverise to a momentary arc over the sharpened tip of the test probe,heating the surface of the probe tip. Since many metals, such as brassand steel, possess positive resistive temperature coefficients, theirresistivity may increase upon the occurrence of an arc. A multi-metermeasurement immediately following such an arc may experience increasedtest probe resistance that gives rise to measurement error. In additionto arc heating, a substantial current flow through the sharpened tipduring a measurement may give rise to resistive heating that alsocreates increased resistivity, building on any preceding arc heating andcausing more measurement error. For example, a sharpened tip comprisedof a metal having a positive temperature coefficient may be required toconduct the flow of 100 amps through a very small volume of metal,generating heat and increased resistance, and subsequently measurementerror. For example, a 100° C. increase in the temperature of the tip ofa copper test probe having a temperature coefficient of 0.0043/° C.causes tip resistance to increase by 43% (i.e., 100×0.0043), and causingan increase in overall test probe resistance.

Another problem that may arise during measurements involving aconductive test probe relates to the arc detection circuitry disclosedin the above-mentioned application Ser. No. 13/404,644. During arcdetection, high frequency spectra may be analyzed for evidence of arcinginternal to the circuitry being powered and measured by the testequipment. The test may be terminated by a circuit breaker upondetection of an internal arc. The accuracy of the measurement depends ona fast rise time in the voltage or current, which requires a small testprobe resistance. However, the occurrence of test probe arcing mayinterfere with the internal detection of arcing by interfering with thesense threshold causing arcing to increase before the sense threshold isachieved. Additionally, as the test probe resistance increases furtherand the rise time gets progressive slower, the response may eventuallybecome so delayed that the circuit breaker does not shut down at all,posing a fire hazard to a circuit that is external arcing.

A further cause of excessive test probe resistance may be the use oftest probe geometries that generate high resistive losses. For example,the sharpened tip of the test probe may be the location of highestcurrent density and may thereby contribute excessively to the overalltest probe resistance if there is a long path from the probe tip to aconductive portion of the test probe having relatively low currentdensity. In addition, local heating may occur near the tip due tocurrent flow, further increasing path resistance.

As can be seen, there exists a need in the art for a durable conductivetest probe that can withstand arcing over many cycles under high currentconditions. Additionally, there exists a need in the art for a testprobe that maintains a low resistance at high currents during arcing sothat measurement resolution and accuracy are maintained. Furthermore,there exists a need in the art for a test probe that preserves the risetime of arc detection circuitry by preventing an increase in test proberesistance caused by arcing. There also exists a need in the art for atest probe that can withstand many contact cycles under live circuitconditions. In addition, there exists a need in the art for a conductivetest probe that has a compact (i.e., small) geometry that minimizes testprobe resistance.

BRIEF SUMMARY

The above-noted needs associated with conductive probes are specificallyaddressed and alleviated by the present disclosure which, in anembodiment, provides a conductive probe having a probe body forcommunicating with a circuit tester or a jumper. The probe body may becomprised of metal and has a free end. A probe tip comprised ofthorium-tungsten may be mounted to the free end of the probe body. Theprobe tip may be configured for contacting a circuit node.

Also disclosed is a conductive probe that may comprise a probe body forcommunicating with a circuit tester or a jumper. The probe body may becomprised of metal and may have a socket formed in a free end. A probetip may be comprised of thorium-tungsten and may have a buried endmounted within the socket of the probe body. The socket may be shapedand sized complementary to the buried end in order to minimize thecontact resistance between the probe body and the probe tip. The probetip may have a narrowed end located opposite the buried end. Thenarrowed end may be narrowed to a contact surface for contacting acircuit node. The shortest distance between the contact surface and theprobe body may be less than approximately 0.250 inch.

Also disclosed is a durable tip that may comprise a probe tip receivableby a probe body configured for communicating with a circuit tester or ajumper. The probe tip may be comprised of thorium-tungsten and may havea buried end that may be receivable by the probe body in such a mannerthat contact resistance between the probe tip and the probe body isminimized. The probe tip may have a narrowed end located opposite theburied end. The narrowed end may be narrowed to a contact surface forcontacting a circuit node. The shortest distance between the contactsurface and the probe body may be less than approximately 0.250 inch.

The features, functions and advantages that have been discussed can beachieved independently in various embodiments of the present disclosureor may be combined in yet other embodiments, further details of whichcan be seen with reference to the following description and drawingsbelow.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features of the present disclosure will become moreapparent upon reference to the drawings wherein like numbers refer tolike parts throughout and wherein:

FIG. 1 is a perspective view of an embodiment of a circuit tester havinga conductive probe attached thereto.

FIG. 2 is an exploded side view of an embodiment of a conductive probehaving a probe plug for mating with a circuit tester having a probejack.

FIG. 3 is a side view of an embodiment of the conductive probe of FIG. 2mated to the circuit tester.

FIG. 4 is a perspective view of an embodiment of a conductive probe.

FIG. 5 is an exploded sectional view of an embodiment of a conductiveprobe comprising a probe body and a probe tip.

FIG. 6 is a sectional view of the conductive probe of FIG. 5 showing theprobe tip mated to the probe body.

FIG. 7 is an end view of the embodiment of the conductive probe of FIG.6.

FIG. 8A is a side sectional view of an embodiment of a conductive probein a ready position above a circuit node to be measured.

FIG. 8B is a side sectional view of the conductive probe in contact withthe circuit node to be measured.

FIG. 8C is a side sectional view of the conductive probe in energizedcontact with a circuit node and illustrating the density of current flowthrough the probe tip.

DETAILED DESCRIPTION

Referring now to the drawings wherein the showings are for purposes ofillustrating various aspects of the present disclosure, shown in FIG. 1is an embodiment of a circuit tester 31 coupled to a conductive probe 10for the purpose of making electrical contact with a circuit to bemeasured. Circuit tester 31 may comprise a multi-meter electricalcircuit tester or other electrical test equipment or test device such asmay be used to diagnose or repair an electrical circuit. Probe body 11may conduct an electrical signal (not shown) between circuit tester 31and probe tip 15. The narrowed end 14 of probe tip 15 may be narrowed inat least one dimension relative to a contact surface 25 so that theprobe tip 15 is capable of piercing the electrical insulation of a wireor to facilitate reliable contact of the probe tip 15 with a circuitnode (not shown) such as an exposed electrical terminal. Although theprobe tip 15 is shown having a conical narrowed end 14 (e.g., narrowedin two dimensions), the probe tip 15 may be provided with alternativegeometries, such as a blade configuration (not shown) or a multipleprong configuration (not shown). In this regard, the probe tip 15 may beconfigured to achieve a low contact resistance with a circuit node whileminimizing the electrical resistance of the conductive probe 10.

In an embodiment, the circuit tester 31 (e.g., FIG. 1) may be configuredto supply current to conductive probe 10 while retrieving and displayingmeasured electrical parameters such as voltage, current, resistance,frequency, or digital information. For example, a technician operatingthe circuit tester 31 may press an actuating button (not shown) to begincurrent sourcing to provide current to a circuit under test, preferablyafter contacting the probe tip 15 with the circuit node (not shown)under test. However, in embodiments, a technician may prematurelyactuate current sourcing from circuit tester 31, making contact withwhat may be called a live (i.e., energized) circuit, and which mayresult in adverse consequences, as will be discussed below.

Referring still to FIG. 1, in an embodiment, the probe body 11 may befabricated of brass, steel or other suitable metallic material orconductor and which may have a relatively low resistivity. Circuittester 31 and conductive probe 10 may be configured to receive or supplyrelatively high current flows such as, for example, currents ofapproximately 10 to 100 amps or more, and which may be particularlyrelevant in the field of automotive electronics. At such relatively highcurrent flows, it is preferable that the conductive probe 10 provides avery low resistance path in order to avoid excessive ohmic losses whichmay result in measurement errors such as measurement errors by thecircuit tester 31.

At automotive voltages of approximately 12 volts and higher, electricalarcing may occur between the narrowed end 14 and a circuit node (notshown) being contacted, such as when making or breaking contact in thepresence of voltage (live contact). The effect of arcing at narrowed end14, especially when relatively high current flows are available, may bea breakdown, melting, or other damage to the material of the conductiveprobe 10. Such material breakdown may result in permanent andprogressively higher resistance to test currents flowing throughconductive probe 10, and consequently may cause stronger arcs andmulti-meter (e.g., circuit tester 31) measurement errors. Since narrowedend 14 may have a substantially smaller width than probe body 11, probetip 15 may dominate the overall resistance of conductive probe 10.Therefore, resistance increases in probe tip 15 caused by arcing damagemay substantially increase the resistance of conductive probe 10. Forexample, brass, steel, and other conductors having relatively low tomoderate melting temperatures may be particularly susceptible to tipdamage during arcing. In this regard, while brass, steel, and otherconductors or materials may meet the resistivity requirements of highcurrent flows, such materials may not provide for a durable probe tip15, and may cause measurement errors.

Referring now to FIG. 2, shown is an embodiment of a conductive probe 10configured with a probe plug 33 for electrically mating with circuittester jack 34 of circuit tester 31. The mating of the outer surface ofprobe plug 33 to the inner surface of circuit tester jack 34 may providea low contact resistance to prevent measurement error, yet may allow foreasy replacement of conductive probe 10. While a plug and jackarrangement is shown in this embodiment for attaching the conductiveprobe 10 to the circuit tester 31, it is to be understood that otherforms of temporary or permanent attachment are possible. For example,the conductive probe 10 may be attached to a circuit tester by means ofa threaded attachment or by means of sliding fit. In a furtherembodiment not shown, the probe and jack assignments may be reversed,with the conductive probe 10 being outfitted with a jack instead of aprobe plug 33, and the circuit tester 31 being outfitted with a pluginstead of a circuit tester jack 34.

Referring still to FIG. 2, an embodiment of a conductive probe 10comprises probe body 11 which may conduct electrical current betweenprobe plug 33 and probe tip 15 mounted to the end of probe body 11. Inan embodiment, buried end width 20 (FIG. 5) may define the diameter of aburied end (not shown) of probe tip 15 that may be sized and configuredfor an interference fit within the probe body 11. In an embodiment,narrowed end 14 may be conical in shape for contacting a circuit node(not shown) to be measured. Probe tip 15 may be comprised ofthorium-tungsten having an immunity to material breakdown in thepresence of electrical arcing, and which may have a relatively highmelting temperature. For example, thorium-tungsten may have a meltingtemperature of approximately 3410° C. Probe body 11 may be comprised ofa low-cost conductor material having relatively low resistivity. In anembodiment, the probe body 11 may be formed of any one of a variety ofdifferent metallic materials, without limitation, including brass,copper, steel, or other metallic materials or alloys thereof.

Probe tip 15 may be sized and configured to provide a relatively shortdistance, i.e., a shortest distance 23 (FIG. 6), between contact surface25 and a free end of the probe body 11. For example, the probe tip 15may provide a shortest distance 23 in an embodiment wherein the probetip 15 is press fit into the probe body 11. Because thorium-tungsten mayhave substantially higher electrical resistance than the material of theprobe body 11, the shortest distance 23 may advantageously limit theoverall path resistance through conductive probe 10 to be less than themeasurement resolution required by circuit tester 31, thereby preventingmeasurement errors. Furthermore, the connection of the thorium-tungstenprobe tip 15 to the low-resistivity probe body 11 along the shortestdistance 23 advantageously provides for a durable conductive probe 10capable of conducting high current flows and withstanding arcing withoutdegradation or damage to the probe tip 15 or probe body 11.

In FIG. 2, the shortest distance 23 may be along a conical surface ofthe probe tip 15 assuming that the core of probe tip 15 extends intoprobe body 11 by a greater distance. It is to be understood however thatthe probe tip 15 may be provided in other geometries, shapes, orconfigurations, and/or in other mounting styles and which may alter thelength of the shortest distance 23 between the contact surface 25 andthe portion of probe body 11 nearest the contact surface 25. Forexample, a butted connection (not shown) between probe tip 15 and probebody 11 may define an axial path (i.e., along a direction parallel to anaxis of the conductive probe) of the shortest distance 23. In anembodiment, shortest distance 23 may be less than approximately 0.250inch in order to maintain a sufficiently low resistance for conductiveprobe 10. In another embodiment, shortest distance 23 may be less thanapproximately 0.100 inch. However, shortest distance may be larger than0.250 inch. Additionally, gold plating (not shown) may be applied to theprobe tip 15 to improve contact resistance of the surface of the probetip 15 or to prevent corrosion of the probe tip 15.

Referring still to FIG. 2, in an embodiment, the thorium-tungsten of theprobe tip 15 may have a concentration of between approximately 0.5% andapproximately 5% (percent) thorium by weight, the remaining weight beingtungsten. More typically, the concentration of thorium may beapproximately 1-2% by weight. However, the thorium-tungsten of the probetip 15 may be provided in any concentration of thorium by weightrelative to the tungsten. Thorium, a radioactive material, may be addedto tungsten in a process of doping using thorium oxide, or the thoriummay be added to tungsten using other techniques known in metallurgy.Thorium-tungsten may also be referred to as thoriated-tungsten. Addingthorium to tungsten may increase the current-carrying capacity of thetungsten by approximately 20% to 50%, enhancing the ability of the probetip to conduct high current flows in the presence of arcing withoutmaterial damage. Thorium may also increase tungsten's emissivity invacuum tubes.

Performance tests on a 2% thoriated-tungsten probe tip 15 that was pressfit into a brass probe body 11 demonstrated that the thoriated-tungstenprobe tip 15 may have substantial immunity to material break down duringarcing and 100 amp current availability. After repeated cycles of livecontact of the probe tip 15 to a brass conductor wherein arcing wasobserved, the thoriated-tungsten probe tip 15 exhibited no measureableincrease in the resistance of the conductive probe 10, demonstratingthat thorium-tungsten advantageously serves as a durable material forprobe tip 15. Furthermore, the performance tests demonstrated that thefunctioning of arc detection circuitry (e.g., of circuit tester 31) isunimpaired by the use of the thoriated-tungsten probe tip 15.Advantageously, the use of a compact press fit geometry of the probe tip15 into the probe body 11 minimized the electrical resistance ofconductive probe 10 to an amount below the measurement resolution. Theperformance tests of the probe tip demonstrated that the objectives ofmeasurement accuracy, high resolution, arc immunity, proper arcdetection, and non-interference with the operating point of the circuitunder test may be achieved with a balanced thorium-tungsten design.

During the measurement of high current flow, and during arcing, localheating of probe tip 15 may temporarily raise the test probe resistancefor probe tip materials having a positive temperature coefficient. Forexample, the thermal coefficient of electrical conductivity ofthorium-tungsten may be approximately 0.0045/° C. compared toapproximately 0.0015/° C. for brass, meaning that the electricalresistance of thorium-tungsten may be much higher than the electricalresistance of brass when resistively heated. However, by using a probetip 15 having a compact geometry (e.g., a relatively small size orvolume), a low resistivity material for the probe body 11, and ashortest distance 23 between the probe tip 15 and the probe body 11, abalance in performance attributes may be achieved, including relativelyhigh measurement resolution, improved durability of the probe tip in thepresence of repeated arcing, relatively low cost, and relatively fastrise time performance for arc detection circuitry. Advantageously, inthe performance tests mentioned above, neither arc heating nor resistiveheating were measurably occurring.

Referring to FIG. 3, shown is an embodiment of a conductive probe 10electrically and mechanically mated via probe plug 33 to circuit tester31 by inserting probe plug 33 into circuit tester jack 34. In anembodiment, the probe plug 33 may be slidably inserted into the circuittester jack 34 or the probe plug may be threadably engaged (not shown)to the circuit tester 31. The mating of the outer surface of probe plug33 to the inner surface of circuit tester jack 34 may provide a lowcontact resistance which may minimize measurement error, yet allow foreasy replacement of conductive probe 10. Probe body 11 may, by virtue ofa relatively large diameter shaft, provide a low resistance path toprobe tip 15 between contact surface 25 and probe body 11. Probe tip 15extends from buried end width 20 to narrowed end 14 and may be conicalin shape, or may have some other shape to facilitate contact of theprobe tip to a circuit node (not shown). In an embodiment, the probe tip15 may have a sharpened end terminating in a point or otherwise shapedto make reliable contact with a circuit node. The probe tip 15 may beconfigured to provide a shortest distance 23 between contact surface 25and probe body 11 which may limit the resistance contribution from aprobe tip 15 comprised preferably of thorium-tungsten, allowing goodmeasurement resolution under all test conditions.

The conductive probe 10 may be comprised substantially of probe body 11made from a material of relatively low electrical resistivity in orderthat a relatively compact volume of thorium-tungsten may be used forprobe tip 15. In one embodiment, at least approximately 80% by volume ofthe conductive probe 10 may be comprised of the probe body 11. Inanother embodiment, approximately 97% of the conductive probe 10 may becomprised of the probe body 11, the remaining approximately 3% of thevolume comprising the probe tip 15. It is to be understood that thisdisclosure is not limited to the above-mentioned proportions of probebody volume to probe tip volume. In this regard, the conductive probe 10may be provided in any proportion of probe body volume to probe tipvolume that provides a balance of a low conductive probe resistance withrelatively high durability of the probe tip under arcing and highcurrent flows.

Referring still to FIG. 3, portions of the probe body 11 may be enclosedin an insulating layer (not shown) for preventing unintended electricalshorting to the test environment. Furthermore, a portion of the probebody 11 may be enclosed with a handle (not shown) for handling theconductive probe 10 conveniently. The handle (not shown) and insulatinglayer (not shown) functions may be combined. Additionally, circuittester 31 may be replaced with a jumper or test lead suitable forestablishing a temporary connection between the circuit node incommunication with contact surface 25 and another circuit node in thesame or another electrical circuit. In this regard, the probe tip 15 andprobe body 11 configuration disclosed herein may be installed on orintegrated into a jumper or a test lead. As indicated above, thethoriated-tungsten composition of the probe tip 15 may advantageouslyminimize degradation or damage that may otherwise occur in aconventional probe tip such as due to arcing.

Referring now to FIG. 4, shown is a cutaway perspective view of anembodiment of probe body 11 including a probe tip 15 which may include acylindrically-shaped buried end (not shown) and including a conicalshape narrowing to a narrowed end 14. In an embodiment, the buried end(not shown) of probe tip 15 may have a buried end width 20 that mayextend into an interior of the probe body 11. The buried end of theprobe tip 15 may extend far enough into the probe body 11 such that theshortest distance 23 between the probe tip 15 terminal end and the probebody 11 is measured along the surface of the probe tip 15. As may bemore evident in FIG. 4, thorium-tungsten probe tip 15 may have agenerally compact geometry and a small volume relative to probe body 11,and which may advantageously give rise to a small path resistancethrough probe tip 15 and probe body 11.

Referring now to FIG. 5, shown is an exploded side sectional view of anembodiment of the conductive probe 10. Probe tip 15 may have a buriedend 13 that may be sized to provide a press fit into the socket 16 alonginterference fit surface 12 within probe body 11. As indicated above,the probe body 11 may be configured to communicate with (e.g., ismounted to or integrated with) a circuit tester, a jumper or test lead,or other electrical device or electrical component. Buried end 13 mayhave a buried end length 19 that may be greater than or approximatelyequal to socket length 18 along interference surface 12. Buried endwidth 20 may be sized to form an interference fit of from approximately0.0001 inch to approximately 0.005 inch with socket 16. For example, fora buried end 13 width of approximately 0.250 inch, the socket 16 mayhave a diameter of approximately 0.249 inch. The buried end 13 width andthe socket 16 width (e.g., diameter) may be such that a negligiblecontact resistance occurs between probe tip 15 and probe body 11, andsuch that the probe tip 15 is retained within the probe body 11. Probetip 15 may be sharpened or shaped to a narrowed end 14, terminating atcontact surface 25 and being configured for piercing an insulatedelectrical wire (not shown) and/or for penetrating an exposed electricalterminal (not shown). However, the probe tip 15 may be provided in anyone of a variety of alternative shapes and configurations configuredcomplementary to a specific application. For example, the probe tip 15may be provided with a generally blunt or flattened terminal end (notshown), a generally rounded end (not shown), a multi-pronged shape, orother shapes, and is not limited to the conical shape of the probe tip15 shown in the figures.

Although FIG. 5 may suggest that the buried end 13 and socket 16 has acylindrical shape, the buried end 13 and socket 16 may be provided inother geometries. For example, buried end 13 and socket 16 may berectangular (not shown), square, or other faceted cross-sectionalshapes, or buried end 13 and socket 16 may be axially splined (notshown), helically threaded, ribbed, or provided with other mechanicalsurface features for interlocking the probe tip 15 to the probe body 11.Alternatively, probe tip 15 may be provided with a socket (not shown) tomate with a plug (not shown) that may be formed on an end of the probebody 11. In one embodiment, buried end 13 may have a buried end width 20of less than or no greater than approximately 0.250 inch for the purposeof minimizing the distance between contact surface 25 and the nearestportion of probe body 11. In another embodiment, buried end 13 may havea buried end width 20 of approximately 0.097 inch. In a furtherembodiment, buried end 13 may have a buried end width 20 ofapproximately 0.125 inch. In this regard, the buried end 13 of the probetip 15 may be provided in any buried end width 20, without limitation.In an embodiment, the ratio of buried end width 20 to socket length 18may preferably range from approximately 1:1 to approximately 3:1. Inanother embodiment, the ratio of buried end width 20 to socket length 18may preferably be approximately 2:1. However, the probe tip 15 and probebody 11 may be configured to provide any ratio of buried end width 20 tosocket length 18.

In an embodiment (not shown), the buried end length 19 may be greaterthan the socket length 18 which may result in the start of the narrowedend 14 protruding (not shown) past the end of the probe body 11 by morethan the length of the conical portion of probe tip 15, leading to anincreased distance between contact surface 25 and the free end of probebody 11 nearest the contact surface 25. Such protrusion of probe tip 15beyond free end of probe body 11 may be desirable in extending a narrowtip deeper into a cramped region of circuitry to be tested. In the casewhere the start of the narrowed end 14 protrudes past the end of theprobe body 11, the shortest distance (not shown) between the contactsurface 25 and the nearest portion of the probe body 11 may be along aninterior of the probe tip 15 and not along an outer surface of probe tip15.

Referring to FIG. 6, shown is a side sectional view of an embodiment ofthe conductive probe 10 showing the buried end 13 of the probe tip 15press fit into the probe body 11. The probe tip 15 is engaged to theprobe body 11 along an interference fit surface 12 having an engagementlength 22. The probe body 11 may be configured to communicate with acircuit tester or jumper as indicated above.

Referring to FIG. 7, shown is an end view of an embodiment of the probetip 15 mated to the probe body 11. As indicated above, the probe tip 15may be press fit into the probe body although other engagementconfigurations (e.g., threaded engagement or other mechanicalinterlocking) are possible. In an embodiment, the probe tip 15 may havea buried end width 20 that may be less than an outer diameter of theprobe body 11. Probe tip 15 may be sharpened to a pointed contactsurface 25 for contacting an electrical circuit to be tested. In afurther embodiment, the contact surface 25 of the probe tip may beprovided with multiple prong points, a blade having a narrowed linearedge, or other geometries which simultaneously provide for lowelectrical contact resistance with a circuit node (not shown) and lowelectrical path resistance within probe tip 15.

Referring to FIGS. 8A, 8B, and 8C, shown are embodiments of a conductiveprobe 10 in progressive stages of interacting with a circuit node 24 ofan electrical path 27. Circuit node 24 may be an insulated wire or anexposed electrical terminal or any other electrical system, electricaldevice, electrical assembly or electrical component. As indicated above,the buried end 13 of the probe tip 15 may be press fit into the probebody 11 along engagement length 22. In the embodiments shown, the probetip 15 may be shaped to have a narrowed end 14 terminating at thecontact surface 25. Shortest distance 23 may provide the lowestresistance path from contact surface 25 to the nearest portion of probebody 11.

Referring to FIG. 8A, shown is an embodiment of the conductive probe 10in a “ready” position hovering over circuit node 24 in an unpowered(i.e., non-energized) state. No current is flowing through conductiveprobe 10, and electrical path 27 may or may not be energized.Advantageously, the probe tip 15 may be comprised of thorium-tungsten towithstand any arcing that may occur in the “ready” position when theprobe tip 15 is in relatively close proximity to the circuit node 24.

Referring to FIG. 8B, shown is an embodiment of the conductive probe 10unpowered and in a “contact” stage. The contact surface 25 of the probetip 15 is shown contacting the circuit node 24. No current is flowingthrough conductive probe 10, and the electrical path 27 may or may notbe energized.

Referring to FIG. 8C, shown is an embodiment of the conductive probe 10in an “energized” stage wherein contact surface 25 of the probe tip 15is contacting circuit node 24. In an embodiment, the circuit tester 31(FIG. 2) may be engaged to transmit electrical current to the circuitnode 24, creating lines of uniform current density 26. In anotherembodiment, electrical path 27 may be energized and circuit tester 31may receive electrical current from the electrical path 27 as part ofthe measurement being performed, and resulting in lines of uniformcurrent density 26 in the probe tip 15. Lines of uniform current density26 may be most closely packed along the shortest distance 23 path andmore loosely packed along an axial direction of the probe tip becausethe axial path is a longer distance to the probe body 11 than theshortest distance 23, and because the axial direction may have greaterelectrical resistance, and hence is less preferred by flowing electrons.

Referring still to FIG. 8C, the size, shape, configuration, and/orgeometry of the conductive probe 10 (e.g., the probe body 11 and/orprobe tip 15) may be optimized by evaluating the lines of uniformcurrent density 26 in the probe tip 15. In this regard, the geometry forthe conductive probe 10 may be selected to minimize the distance (i.e.,shortest distance 23) between the contact surface of the probe tip 15and the portion of the probe body 11 nearest the contact surface 25,thereby minimizing the resistance of conductive probe 10. In addition,the conductive probe 10 may be configured in consideration of the amountof surface area at the interface between the probe tip 15 and the probebody 11. For example, a larger surface area of the interference fitsurface 12 may generate a smaller electrical resistance for theconductive probe 10, and a smaller amount of surface area of theinterference fit surface 12 may result in a larger electrical resistancefor the conductive probe 10. In addition, the electrical current may bemade to flow in either direction with both directions providing the sameelectrical path.

Additional modifications and improvements of the present disclosure maybe apparent to those of ordinary skill in the art. Thus, the particularcombination of parts described and illustrated herein is intended torepresent only certain embodiments of the present disclosure and is notintended to serve as limitations of alternative embodiments or deviceswithin the spirit and scope of the disclosure.

What is claimed is:
 1. A conductive probe, comprising: a probe bodyconfigured for communicating with a circuit tester or a jumper, theprobe body comprising metal and having a free end; a probe tipconfigured for contacting a circuit node, the probe tip mounting to thefree end; and the probe tip being comprised of thorium-tungsten.
 2. Theconductive probe of claim 1, further comprising: a probe plug; and theprobe body being removably engageable to the circuit tester or thejumper via the probe plug.
 3. The conductive probe of claim 1 wherein:the probe tip is approximately 0.5-5.0 percent thorium by weight.
 4. Theconductive probe of claim 1 wherein: the probe tip is conical in shape.5. The conductive probe of claim 1 wherein: the probe tip is narrowed toa contact surface for contacting a circuit node.
 6. The conductive probeof claim 5 wherein: the probe tip is configured such that a shortestdistance between the contact surface and the probe body is less thanapproximately 0.250 inch.
 7. The conductive probe of claim 5 wherein:the probe tip is configured such that a shortest distance between thecontact surface and the probe body is approximately 0.100 inch.
 8. Theconductive probe of claim 1 wherein: the probe body is comprised ofbrass.
 9. The conductive probe of claim 8 wherein: the probe body is atleast approximately 80 percent of the conductive probe by volume. 10.The conductive probe of claim 1, further comprising: a gold platingapplied to the probe tip.
 11. A conductive probe, comprising: a probebody configured for communicating with a circuit tester or a jumper, theprobe body comprising metal and having a free end; a socket being formedin the free end; a probe tip having a buried end and a narrowed endlocated opposite the buried end, the buried end being mountable withinthe socket, the socket being shaped and sized complementary to theburied end in order to minimize contact resistance therebetween, thenarrowed end being narrowed to a contact surface for contacting acircuit node; the probe tip being comprised of thorium-tungsten andbeing configured such that a shortest distance between the contactsurface and the probe body is less than approximately 0.250 inch.
 12. Atip for a conductive probe, comprising: a probe tip receivable by aprobe body configured for communicating with a circuit tester or ajumper, the probe tip having a buried end and a narrowed end locatedopposite the buried end; the buried end being receivable by the probebody in such a manner that contact resistance between the probe tip andthe probe body is minimized; the narrowed end being narrowed to acontact surface for contacting a circuit node; the probe tip beingcomprised of thorium-tungsten and being configured such that a shortestdistance between the contact surface and the probe body is less thanapproximately 0.250 inch.
 13. The tip of claim 12 wherein: the probe tipis approximately 0.5-5.0 percent thorium by weight.
 14. The tip of claim12 wherein: the probe tip has a conical shape.
 15. The tip of claim 12wherein: the shortest distance between the contact surface and the probebody is approximately 0.100 inch.
 16. The tip of claim 12 wherein: theburied end is sized to provide an interference fit with a socket formedin the probe body.
 17. The tip of claim 16 wherein: the buried end has awidth of no greater than approximately 0.250 inch.
 18. The tip of claim16 wherein the buried end has a width of one of the following:approximately 0.097 inch; and approximately 0.125 inch.
 19. The tip ofclaim 12 wherein: the buried end of the probe tip has a cylindricalshape.
 20. The tip of claim 12, further comprising: a gold platingapplied to the probe tip.